#include <stdio.h>
#include <unistd.h>

int g_val = 100;

int main()
{
    pid_t id = fork();
    if(id == 0)
    {
        int cnt = 0;
        //child
        while(1)
        {

            printf("I am child, pid: %d, ppid: %d, g_val: %d, &g_val: %p\n",\
                    getpid(), getppid(), g_val, &g_val);
            sleep(1);
            cnt++;
            if(cnt == 5)
            {
                g_val = 200;
                printf("child chage g_val 100 -> 200 success\n");
            }
        }
    }
    else 
    {
        //father
        while(1)
        {
            printf("I am father, pid: %d, ppid: %d, g_val: %d, &g_val: %p\n",\
                    getpid(), getppid(), g_val, &g_val);
            sleep(1);
        }
        
    }
}
